Not necessarily. If you end the call using moderator controls, then the audio conference will end. If you are disconnected, you may be able to dial back into the conference.
During a web conference, a disconnection is indicated by a red Network icon above the toolbar. When a disconnection occurs the conference tries to reconnect you automatically. If you find a Reconnect button on your conference toolbar, clicking that will attempt to reconnect you as well. Finally, if the connection cannot be re-established, a page will display providing instructions to re-launch your browser to get back into the conference. If you need to do this, your attendees will still be present in the conference.